New users can:
Post an answer to provide information that answers the question.
Edit an answer to add a little information or correct a minor mistake.
Ask a new question if they want explanations about an answer.
That covers a vast majority of cases. In the rare cases where a comment would really be the right thing, there is a way to sneak it in: ...
I see 3 problems with your proposal:
The danger is that someone won't post an actual answer because it is already contained in a well-written comment. Or when someone says the same thing, it is seen as plagiarism.
Comments cannot be downvoted, which means that comments then have to be responded to when the commenter is wrong or unhelpful, which can end up ...
This is absolutely not going to happen. It has been discussed many times on meta.se and the cons far outweigh the pros. These include revenge voting, leveraging pressure, general nastiness etc.
We can encourage people to comment, but can't force them to. It costs rep to down vote so they are doing so for a reason. It can be harder identifying that reason if ...
No - this is by design.
If you have a reply to something a commenter has asked, respond to them. For another commenter, reply to them separately.
Remember, though, comments are supposed to be brief and temporary, and used to gain clarification of a point - plan for having them deleted.
The de facto practice on this site (and for most of SE) has always been to remove comments. They are absolutely considered temporary, and only useful if they help an answer get updates or edits for clarification.
Those comments were not useful at all - Motivated added basically the same comment to every post, which just adds noise, especially as the comment ...
If you want clarification on an answer, asking in a comment is what you should do.
However, if you want to extend the scope of the answer or ask about how the answer applies in another context, then it is likely that you are asking a separate question.
While in general I agree - this is an English speaking site and we should ensure that all comments etc are in English - in this specific instance Shikata ga nai is the name of the tool that the editor correctly edited in to the post, along with some other good edits. So I wouldn't be too concerned this time.
To the editor - please stick to English next time....
IMO, you answered your own question:
I've done all of these depending on how much the comment contributes.
For guidance, let's look at the conventions of citations in academic papers. In parallel to your list, I've seen all of the following:
"In their seminal 1984 work on DoHickeys, Smith, Doe, and Li showed that DoHickeys have great foobar properties."
The purpose of comments is to request clarity or provide information that should then cause a post to be updated.
Comments are not for anything permanent.
If mods have time when deleting comments or moving them to chat we will keep highly voted comments longer than others, but generally if there is a long thread that gets flagged to us we move it to chat ...
Some of my personal thoughts:
As far as I know, converting answers to comments and vice versa is allowed to 10k rep. users.
Ok, this is false - thanks @grawity.
Personally, I think that merging this privilege with 3k rep. (close and reopen votes) or 10k tools could help solve problems quicker.
New users cannot post ...
I was the one who made the edit. I had meant to have the edit comment to explain that I corrected the spelling by using something like 仕方が無い - Shikata ga nai, but for some reason I just posted the Japanese text and not the romaji. Not sure why, I must have been in a hurry. It was my bad.
As @Xavier59 and @AviD explains in comments, this is not a bug.
When a moderator converts an answer to a comment, all the comments to the answer are moved along with it. In this case the moderator didn't notice the autocomment, and it was automatically moved to the question. So nothing strange going on at all.
I am a relatively new user to stackexchange in general and my opinion is that actual answers are better than comment answers in more than just one way. Although good information can come from comments, it doesn't fully answer the question as you said and if the question-asker follows up with that comment it can be ambiguous whether or not the question was ...
I have to admit I am absolutely guilty of this.
The reason why I do it is because my answers usually tend to be a bit longer, and I like to put in references for my claims. Of course, I'm sure you will find plenty of answers of mine that are short and have no references, but in general that's what I do.
But sometimes I don't have the time. Sometimes I'm on ...
The two main reasons why comments are restricted to 50+ rep users are:
Ensuring that the user has demonstrated sufficient understanding of our system before they're allowed to comment (to avoid new users posting e.g. "Thank you JukEbox, your answer worked for me! But I have another problem now: ... Can you help me?")
Now, obviously, ...
New users are deliberately not allowed to post comments (except under their own posts), precisely to avoid what you're trying to do. This is a question and answer site. Comments distract from the main purpose of the site.
Stack Exchange was explicitly designed to avoid the problems of forums where the conversation drifts, the useful answer is somewhere in ...
Not a bug - a feature. It's a way to keep spam down to a minimum. Answers persist but comments can disappear forever. If a 1-rep new account is created to spam, it becomes high-visibility so that action can be taken.
The rep threshold (50) is low enough to allow people to quickly build enough rep in order to comment.